The state of the art covers multi-needle quilting machines employed in the textile industry to make quilted products with the knotted-stitch technique.
These quilting machines generally comprise:
an inlet assembly to feed the multi-layered fabric which is to be quilted, for example consisting of an outer fabric and at least an inner layer of supporting and/or padding material; PA1 a stitching assembly including upper stitching elements and lower stitching elements; PA1 an outlet assembly to collect and/or measure and/or cut the semi-finished quilted product.
The upper stitching elements of the stitching assembly generally consist of parallel longitudinal bars endowed with alternating ascending/descending motion and bearing a plurality of needles which are spaced lengthwise at a fixed distance.
Each of the needles is associated with a respective stitching thread, denominated needle thread, and cooperates with a mating gripping means provided on the lower stitching elements.
Each gripping means has a respective stitching thread denominated bobbin thread.
The gripping means grasp the eyelet or heddle eye, of the needle thread and weave it in the desired manner with the bobbin thread in order to achieve the desired type of stitch.
In quilting machines of this type, with the knotted-stitch, the gripping means can be of two types: shuttle type or the type with rotating hooks (crochet).
In the first system, a plurality of shuttles are used, each one carrying a respective bobbin or spool of thread, which are made to move alternately forwards and backwards on sliding guides with substantially straight movements coordinated with the ascending/descending movements of the needle-carrier bars.
Quilting machines of the shuttle type technology include one, two or three upper needle-carrier bars, each one cooperating with a respective lower row of shuttles.
When three needle-carrier bars are used, only two of them are used at the same time; the two nearest bars are used to make small or average size designs, and the two farthest bars to make large designs.
Given the space occupied by the shuttles, with this type of quilting machine it is possible to make quilted products with designs which are quite complex, but characterized by lines of stitches whose distance cannot be less than the transverse size of the shuttles and/or the space occupied by the sliding guides.
In multi-needle, shuttle-type quilting machines, it is however possible to mount one needle every inch (2.5 cm) on the relative needle bar, so as to achieve, for example, lozenges or diamonds 1 inch across.
However, the great inertia of the alternative motion of the shuttles and the sliding friction of the shuttles on the relative sliding guides limits the highest attainable speed of this type of machine to about 600 stitches per minute.
Shuttle-type quilting machines, moreover, include other disadvantages including rapid wear of the shuttles, over-heating due to friction between the guides and the shuttles, long downtimes to replace the finished bobbins, and also other problems.
Quilting machines with rotating hooks on the one hand do not have the above problems and offer higher productivity due to the higher speeds which can be obtained (up to 1000.div.1200 stitches per minute using rotation guides made of particular anti-friction materials), but on the other hand they do not enable quilted articles with very small designs to be achieved.
This is because of the considerable size of the hooks which prevent a closer positioning beyond the physical limit.
The distance of the lines of stitches is linked to the physical size of the hook itself, and, in machines known to the state of the art, it has therefore never been possible to make, at the same time and with all the lower stitching elements, designs with a distance between the needles of about 2.5 cms (1 inch).
Moreover, because of the considerable space occupied by the hooks and factors connected with the cost of a bar of the hooks, it has not been possible so far to achieve competitive multi-needle quilting machines with more than two rows of hooks, and therefore more than two needle-carrier bars, and therefore it has never been operationally possible to achieve, on the same machine, both large and small designs.
It is known that the stitching pattern is defined by the reciprocal position assumed by the needles with respect to the movement of the material.
This reciprocal position obviously determines the size of the pattern achieved.
For example, in order to make diamond shapes of 6 inches across, two parallel needle bars are used with needles mounted every 6 inches; these needles are staggered and the needles of one bar are intercalated with the needles of the other bar.
The material which is to-be quilted is then moved with a continuous movement forwards-left-right-left, wherein every sideways movement covers a space of three inches, so that the edges of the zig-zag stitches (3 inches wide) made by the needles of the first needle bar touch the edges of the zig-zag stitches (also 3 inches wide) made by the second needle bar, thus creating a continuous quilting of diamonds 6 inches across.
In a similar manner, in order to achieve diamonds 3 inches across, needles separated from each other by a distance of 3 inches must be mounted on the relative needle bars.
In order to achieve larger designs, for example 12 inches across, the machine must have three needle bars separated transversely from each other by 3 inches, wherein the two outer needle bars have their needles separated from each other by 12 inches, and the needles of the first bar are intercalated with the needles of the third bar.
The forwards-left-right-left movement of the material to be quilted will therefore be 6 inches for every step.
The second, intermediate needle bar in this case is excluded from the quilting cycle, but installation costs are considerably increased, given the high costs of the hooks.
Consequently, quilting machines with rotating hooks as are known to the state of the art do not make possible to achieve quilted products with close lines of stitches so as to make attractive designs or patterns which will be requested by consumers.
In such machines moreover, since the rows of lower stitching elements are stationary and very far from each other, in order to vary the size or the profile of the desired design it takes a long time to equip them, particularly to re-insert or replace the bobbin of thread associated with the respective hooks.
To change the size of the design it is necessary to mount a greater or lesser number of needles, and the corresponding hooks, in the prescribed fixed and unchangeable positions at the pre-determined distances on the respective bars.
Document FR-A-1.523.750 shows a multi-needle quilting machine with rotating hooks; the innovation is substantially that the hooks are mounted with their axes parallel to the needle bars, rather than perpendicular, the hooks being supported by oscillating arms so as to enable the bobbin to be replaced quickly.
The hooks, moreover, have toothed rings on the outer circumference which, as they engage mating toothed wheels mounted on a central shaft, make them rotate.
The purpose of FR'750 is to reduce as much as possible the distance between the hooks.
However, the positions of the hooks remain fixed and cannot be changed; moreover, using rotating hooks with an axis parallel to the needle bars makes it impossible to use pairs of needles working with a single hook in order to make double line stitching.
Document JP 71-48366 shows a system to mount eccentrics to drive the needles in a multi-needle quilting machine with one needle bar and rotating hooks, in such a way that the lateral size of the hooks is as limited as possible so as to reduce the distance between two adjacent needles.
In this case too the hooks are mounted with their axis of rotation parallel to the needle bar and their position is fixed and cannot be changed.
U.S. Pat. No. 5,249,536 shows an embroidering machine with multiple heads; the principal innovation is that there is a system to hold and cut the ends of the threads after stitching.
U.S. '536 also shows a system, now abandoned in modern embroidering machines, to make a head-bearing bar pass in order to vary the colour of the thread to be coupled with the fixed needle.
This document has no relevance to the present invention.
U.S. Pat. No. 2,483,466 shows a multi-needle quilting machine with one needle bar, presumably with rotating hooks; the innovation is that there is a mechanical system to move the materials which are to be quilted under the stationary needles so as to achieve patterns of a substantially circular shape.
The position of the hooks is stationary and cannot be changed.
Finally, DE-A-1.146.341 shows a multi-needle quilting machine with one needle bar; the innovation lies in the direction of feed of the materials to be quilted, that is to say, they are fed in the opposite direction to the one used in conventional machines.
In this case too, the position of the hooks is stationary and cannot be changed.
It is clear from the above that not one of the prior art documents is able to provide a solution, even a partial one, to the shortcomings described.